This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Respiratory gasses may be readily distinguished from non-respiratory gasses by carbon dioxide content. Exhaled respiratory gas in a human typically contains between 3% and 5% carbon dioxide. In contrast, ambient air has only approximately 0.03% carbon dioxide. Normal esophageal gas has similarly low levels of carbon dioxide.
The detection of respiratory gasses via carbon dioxide content may be useful in a variety of circumstances. For example, one may determine whether an endotracheal tube has been correctly placed in the trachea rather than in the esophagus by detecting the presence of carbon dioxide in air exiting the tube. If carbon dioxide levels consistent with respiration are present, then the tube is correctly placed. If only low carbon dioxide levels consistent with placement in the esophagus are present, then the tube may have been incorrectly placed and may need to be removed and reinserted correctly. Additionally, if a tracheal tube is present in the trachea, but carbon dioxide levels in respired gas are low, this may be indicative of perfusion failure.
Continued detection of carbon dioxide in respired gas may also be useful in determining if an endotracheal tube has been dislodged and if breathing and perfusion continue to be normal.
Current products can detect carbon dioxide in respired air using various chemicals sensitive to the presence of carbon dioxide on a substrate such as cellulose filter paper, for example Whatman paper.